Ursula K. Le Guin, The Unreal and the Real: Selected Stories, Volume One: Where on Earth

"One of the rocks in my soulbag, a little grey rock that I had picked up on a certain day in a certain place in the hills above the river in the Silver Time, a little piece of my world, that became my world. |Every night I took it out and held it in my hand while I lay in bed waiting to sleep, thinking of the sunlight on the hills above the river, listening to the soft shushing of the ship’s systems, like a mechanical sea"